They both have a lot of ground to make up. I read someplace that Sony has overtaken Nikon for second place amongst full framed cameras, with Canon in their sights (realistic or not, Sony is making a very aggressive push, especially the last few years).
As consumers, its always good to see these camera compete with each other....the more choices we have, the more companies will continue to push the envelope for our $$$.
Canon & Nikon will have to offer something Sony cant. At this point I dont know if thats possible. Way back, people stayed loyal to Canon, Nikon, etc....because they were heavily invested in those systems. Now? Its pretty easy to adapt lenses from other makers and get close to native AF performance....so the selling point for Canon/Nikon won't be that. Itll have to be something else.